It seems kind of silly that while cyclists have been enjoying the benefits of gears for a good number of years, people in wheelchairs have for the most part had to contend with a single 1:1 gear ratio. There is a practical reason for the fixed gear: Cyclists pretty much have have their hands free so they are able to change gears without losing momentum. It's different for wheelchair users. Imagine going up a hill, removing a hand from a wheel to change gears and losing all your momentum. The benefit of the easier gear would be outweighed by the loss of speed. Changing gears without breaking stride would require a massive change in user behavior and a good deal of practice, so it isn't for everyone. The IntelliWheels AGS (Automatic Gear-Shift) system may do just that. The concept is the work of Scott Daigle, an engineering student at the University of Illinois. His system monitors how the wheelchair is being pushed and changes gears automatically to improve performance. Sensors analyze torque, speed and tilt to determine how hard the rider is pushing and the speed and angle at which the wheelchair is traveling. From these variables, IntelliWheels selects the best appropriate gear. While the exact number of wheelchair users that the IntelliWheels system could benefit is up for debate, Daigle's estimation is that it could be as high as 73 percent. Source: Futurity